1. Field of the Invention
This invention relates generally to the placement of intravascular catheters as well as catheters for the administration of regional anesthesia. More particularly, relating to intravascular catheter placement, a system for positioning a catheter for such procedures as central venous pressure monitoring or infusions of fluids or medications. With respect to regional anesthesia, the invention relates to a system for positioning a catheter and nerve stimulator or other needle in conjunction with various procedures, such as, the administration of an anesthetic blockade and for continuous infusion of anesthetic through the catheter.
2. Antecedents of the Invention
The field of regional anesthesia relates to the practice of administering anesthesia to a specific body region during surgery, for the relief of postoperative pain, and for extended relief of trauma or chronic pain. Often, regional anesthesia has been found to be preferable to general anesthesia because of increased safety, the availability of postoperative pain control and decreased anesthetic costs.
Regional anesthesia delivery techniques strove to optimize administration of a local anesthetic in close proximity to a target or nerve plexus so as to establish a neural blockade. Successful administration of regional anesthesia was dependent upon the accurate placement of the anesthetic in relation to the target nerve or nerves.
Various techniques have been employed to assist in placement of an administration needle in close proximity to the target nerve, which was not externally visible. One of the traditional methods of needle placement involved eliciting paresthesia. Among the disadvantages of this technique was the lack of accurate patient responses amongst patients who were disoriented and/or sedated.
A prevalent technique employed the use of nerve stimulators electrically coupled to a nerve stimulator needle. Such method was premised upon the phenomenon that an electrical pulse is capable of stimulating a motor nerve fiber to contract an innervated muscle or cause paraesthesia, in the case of sensory nerve stimulation.
The nerve stimulator needle was placed within the tissue of the patient's body in the vicinity of the nerve to be blocked and then advanced until stimulation of the target nerve was achieved as determined by visually detecting muscle contractions or by eliciting a report that the patient felt the stimulus in response to the current flow through the stimulator needle.
The current supplied by the nerve stimulator was reduced as the nerve stimulator needle was further advanced, until stimulation of the target nerve was achieved using a reduced current level associated with a prescribed distance between the needle tip and the target nerve.
Thereafter, a portion of the anesthetic dose was administered through the needle to terminate the response to the nerve stimulation current. If the response was terminated by the initial administration, the needle was deemed to be properly positioned in proximity to the target nerve and the remaining dose of anesthetic was administered and the needle was withdrawn upon completion of the surgical procedure.
Placement of catheters for continuous infusion of local anesthetics or other drugs during surgical procedures and primarily postoperatively has been achieved by use of an intra-catheter which was placed or threaded through the internal lumen of a larger needle or stiff cannula, or by use of an extra-catheter which was placed or threaded over an internal needle or smaller stiff cannula. Each technique has been associated with certain disadvantages and limitations that have resulted in less than optimal results for achieving successful continuous plexus or nerve block in clinical practice. These disadvantages have severely limited the use of continuous anesthesia or analgesia, resulting in under-utilization of continuous techniques in favor of more predictably successful, less invasive and usually less traumatic and therefore safer nerve or plexus blockade utilizing only a nerve stimulation needle for anesthesia or analgesia administration as previously described.
Problems associated with the use of an intra-catheter included the fact that a very large and therefore more traumatic introducing needle, e.g. 17 or 18, gauge was necessary to allow passage of a smaller usually 19 or 20 gauge flexible catheter. This caused increase pain and discomfort during the placement. The catheter was passed through the bore of the introducing needle with little control of the final position of the distal end of the catheter because the flexibility of the catheter did not allow the practitioner to accurately determine where the catheter will travel once it passed beyond the needle tip.
Stimulating catheters have been developed with a flexible metal stylet inside the catheter which allowed for the ability to electrically stimulate the nerve or nerves, but these too, were difficult to control in terms of the final positioning of the catheter tip once it passed beyond the needle tip.
Another problem with intra-catheter systems has been persistent leaking of the injected medication at the entry point of the removed introducing needle on the skin surface. This occurred because the catheter diameter was smaller than the needle diameter and the diameter of the hole left by the introducing needle. Leakage was especially pronounced after placement of continuous catheters for superficial nerves or nerve plexus.
An additional problem relates to the fact that the catheter passed through a needle does not maintain a predictably straight trajectory once the catheter tip passes beyond the needle tip. This makes visualization of the catheter difficult or impossible when using ultrasonographic imaging to assist in placement of the catheter. A controlled straight trajectory allows precise placement at the proper anatomical position or endpoint when utilizing imaging techniques.
Placement of a catheter through a needle requires the separate attachment of a typically removable hub or mechanism for connecting to larger bore infusion tubing such as intravenous tubing after the external introducing needle is withdrawn over the proximal end of the placed catheter. These affixed hubs have associated disadvantages that include frequent kinking or occlusion of the smaller catheter, disconnection and bacterial or other contamination of the unprotected smaller catheter, or leakage at the connection site.
Major problems associated with the use of an extra-catheter system included the fact that extra-catheters have had to be made of larger gauges than desirable and have been stiffer than desirable to allow adequate stability for advancement over the smaller internal needle. A catheter with the desired flexibility and small diameter was difficult to pass or thread over the needle due to undesired buckling or bending. The length of the extra-catheter was therefore limited because longer extra-catheter systems of very small diameter were too flexible and therefore unstable and difficult to pass. Shorter catheters are not able to reach the more distant desired position required for central venous monitoring or infusions.
The longer a thin catheter or thin needle was, the more unstable it was. This was because each additional unit of length compounded its flexibility. Such catheters would bend when advanced through the skin and deeper tissues, making targeted accurate placement difficult. Additionally, extra-catheters were required to freely slide off of the internal needle, cannula, or stylet and therefore often had undesired movement in relation to the internal needle during use, especially upon advancement and withdrawal. If the extra-catheter was more tightly fitted to the internal needle, withdrawal of the stylet or needle often put undue traction on the catheter, resulting in undesired movement of the catheter tip from the optimal position that was already achieved.
In U.S. Pat. No. 7,699,809, issued to Applicant herein, a system for positioning a catheter that included a nerve stimulator needle carried within the bore of the catheter was described. The needle includes a microelectrode configured as a needle tip protruding beyond the distal end of the catheter. The catheter and needle are fixed against relative axial movement by a releasable clamp which is grasped by the practitioner to compress the catheter bore against the needle without deforming the needle. The clamp is positioned on the catheter at a relatively short distance, e.g. 2 cm, from the skin entry point to minimize flexure when advancing or withdrawing the catheter and needle assembly to simultaneously position the distal end of catheter and needle tip in close proximity to the target nerve or nerve plexus. A plurality of clamps may be employed and each clamp released as it contacts the entry point or a single clamp is released and repositioned after it contacts the entry point.
Upon attaining the desired needle tip position in proximity to the nerve as determined by electrical stimulation, ultrasonographic imaging, etc., a dosage of anesthetic is administered through the needle. With the clamp or clamps fully or partially released so as to fully open the catheter bore, the needle can be freely withdrawn from the catheter. The proximal end of the catheter is thereafter coupled to a syringe, tubing, pump or other device for continuous administration of an anesthetic or other medication.
Presently, 5-6 million central venous catheters (CVC) are placed each year, in the U.S., alone. By contrast to the placement of catheters utilized for regional anesthesia, intravenous catheters require a permanent hub to avoid the serious complication of the accidental placement or migration of the entire catheter into the central or other venous circulation, a so-called “catheter embolization”.
Central venous catheter placements have been performed using a technique that was first described by Seldinger in 1953, now referred to as the “Seldinger Technique”. The Seldinger methodology has been to access the vein with a large-gauge sharply pointed needle, after which a flexible wire was placed through the lumen of the needle. The needle is then removed over the wire following which, a long flexible central venous catheter with a permanent hub was placed over the wire, often after using a scalpel and firm “dilator” to open a space in the skin and underlying subcutaneous tissue, to facilitate the passage of the softer catheter into the vein. The wire was then removed, leaving the catheter in the desired intravascular final position. Needless to say, the procedure was somewhat traumatic and often led to difficulty and contamination during the process of passing the wire and the exchange between needle, wire, and catheter.
Currently, the advocated methodology for central venous catheter placement involves the use of direct ultrasongraphic imaging to guide the initial needle placement into the targeted vein. After needle placement, the ultrasongraphic probe was put down and the remainder of the procedure done under the older, landmark-based methodology that has been used for more than 50 years. The use of ultrasongraphic guidance has improved success rates and decreased complications when compared to the conventional blind landmark-based technique.
Several major medical societies have now endorsed the use of ultrasongraphic guidance for CVC placement. These include the American Society of Anesthesiologists, the American Society of Echocardiologists, the Society of Cardiovascular Anesthesiologists and the Centers for Disease Control and Prevention.
The risk of complications during conventional central venous catheter placement include pneumothorax (0 to 6.6%), carotid artery puncture (6%), subclavian artery puncture (0.5 to 4%), hemothorax (1%), and unsuccessful placement in the internal jugular vein (12%). Central venous catheter associated infections have been identified as a major cause of hospital morbidity and mortality.
The American Society of Anesthesiologists as well as The American Society of Echocardiography with the Society of Cardiovascular Anesthesiologists have recently published guidelines for CVC placement.
While the use of ultrasongraphic imaging during initial placement has reduced complications and additional imaging during catheter placement will further reduce the risk of complications, there remains a need to simplify CVC placement and further reduce the associated risks.